Membrane Potentials

Membrane potentials

Electrical, all cells have them

Regulate cell activity

Synaptic transmission

Chemical

Translates membrane potentials into communication between cells through NTs

Resting membrane potential

Internal neg charge, external pos charge

Na+ and K+ at equilibrium potentials

-71mV

Na+ equilibrium concentrations

15mM inside; 150mM outside

K+ equilibrium concentrations

150mM inside; 5mM outside

What creates membrane potentials

• Na/K ATPase

• Ion leak channels

Ca2+ equilibrium concentration

Inside >> Outside

Cl- equilibrium concentration

Inside >/= Outside

Ion leak channels

Ions flow down concentration gradient

Number cannot change

Number of channels determines permeability of ion

Size of potential

Measured relative to 0

Bigger difference → Larger potential

Depolarization

Membrane potential gets closer to 0 (less negative if still negative; more positive if above 0)

Hyperpolarization

Membrane potential gets farther from 0 (more negative)

K+ equilibrium potential

-91.6mV

Na+ equilibrium potential

+62mV

More cations within the cell…

Positive equilibrium potential

More anions in cell…

Negative equilibrium potential

Membrane potential moves closer to equilibrium potential of the…

Ion with most permeability

Ca2+ equilibrium potential

+133.3mV

Cl- equilibrium potential

-70mV

Action potential phases

Threshold (all or none) → Depolarization → Overshoot → Repolarization → After hyperpolarization → Resting membrane potential